JP-10-59131A proposes an on-vehicle equipment control system. In this system, when a switch provided in a door knob of a vehicle door has been operated, mutual communication is performed between a vehicle unit (main device) and a portable device. When a normal response signal has been received from the portable device, the vehicle door is locked by a door lock/unlock device, which is on-vehicle equipment.
In this system, a low-power request signal and a high-power request signal are transmitted from the vehicle unit to prevent the portable device from being carelessly left in a vehicle compartment when a door is locked. Specifically, a range in which the low-power request signal can be received by the portable device is set to be almost the same as the interior of the vehicle compartment. Therefore, when a response to the low-power request signal is returned thereby confirming reception of the low-power request signal, it can be determined that the portable device has been left in the vehicle compartment.
When no response has been received in response to the low-power signal, a high-power request signal is transmitted to determine whether the portable device transmits a response signal to the high-power request signal. A range in which the high-power request signal can be received is set to include a predetermined range in the outside vicinity of the vehicle. Therefore, when a response is made from the portable device in response to the high-power request signal, the vehicle unit determines that a user carrying the portable device is outside the vehicle, and automatically locks the doors.
When the mutual communication between the vehicle unit and the portable device is performed because the switch provided in the door knob has been operated, the user carrying the portable device is in many cases in the vicinity of the vehicle door to operate the switch.
In this case, for example, the mutual communication between the vehicle unit and the portable unit may be disabled depending on the positional relation with a transmitter or receiver of the vehicle unit and the portable device, for example, when a vehicle body or human body through which radio waves do not easily pass exists between the vehicle unit and the portable device, the mutual communication may be disabled. That is, even within an area in which the mutual communication with the vehicle unit is to be performed, a dead zone area in which the mutual communication is disabled may arise.
When the portable device carried by the user who operates the switch enters and stops in the dead zone area while carrying the portable device, the portable device also remains in the dead zone area. As a result, the user cannot lock the door despite carrying the portable device.
Some of on-vehicle equipment control systems target a vehicle engine for control, and permit and prohibit engine startup based on a result of mutual communication between a vehicle unit and a portable device. In this system, while the portable device is brought into a vehicle compartment by the user, when the storage position of the portable device 1 enters the above dead zone area, the user might not be able to start up the engine despite operating an engine switch.